There is an expression used by the rishonim that one should “fill one’s stomach with shas and poskim.” Shouldn’t it state that one should fill his mind with shas and poskim since one learns Torah with his mind, not his stomach?

The Kotzker Rebbe explains: A few hours after one eats a meal, he wants to eat again. This is the appetite we need for Torah. We should never be satisfied. We should always be thirsty for more.